TOKYO — Triple-digit temperatures have hospitalized 23,000 people just in the past week, nearly double the previous record. Some outdoor pools are too hot for swimming. Construction workers wear battery-powered fans to avoid heatstroke, which has killed 86 people since May.

Even for the stoic Japanese, known for tolerating all manner of discomfort, the summer of 2018 has pushed their limits.

About half the people taken to the hospital this week are older than 65. In Japan — which has a word, “gaman,” that denotes a sense of bearing with it — the elderly are perhaps more susceptible than anyone to feeling they should simply put up with the heat.

Elderly people grew up without air-conditioning, and now that they live on pensions, many are also cost-conscious.

“They think energy conservation is a good thing, especially after the 3-11 disaster,” said Kazuyo Oyamada, the chief consultant at Mizuho Information & Research Institute. She was referring to the Fukushima earthquake and tsunami disaster of March 2011, which led to a shutdown of the nuclear plants that had provided almost a third of Japan’s electricity.

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About half of the people who have been taken to the hospital for heat-related illnesses this past week are older than 65.CreditKo Sasaki for The New York Times

Nevertheless, sales of air-conditioners at Bic Camera, one of the largest electronics chains, jumped close to 70 percent last week compared to the same period a year ago, and not all of those sales can be to the younger generation.

Tokuhiro Shimomura, 76, a retired factory worker who was headed to a hospital in Tokyo on Wednesday for a routine appointment, said he kept the air conditioning on at home, though he worried about the expense.

“Last year I would feel cool in my apartment,” he said. “But this year it is just too hot.”

The pool at the Toshimaen Amusement Park in Tokyo was crowded on Wednesday with families seeking refuge during the first week of the school summer vacation. Scattered across the deck, visitors set up small tents to shield from the sun.

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On the edge of the pool at Toshimaen. Some visitors have set up small tents for shade.CreditKo Sasaki for The New York Times

Noriko Hosoda, 43, sat in the shade wearing a light yellow jacket to protect herself from ultraviolet rays. She was with her two sons and her sister, Kumiko Niizato, 35, who was celebrating her birthday along with Ms. Hosoda’s younger son, Yuzuki, 8.

Ms. Hosoda said this was the first summer her family had kept the air conditioning on all night.

“We can’t sleep without it,” she said. To save money on electricity, the whole family sleeps in one air-conditioned room.

At an elementary school in Sumoto, a city in western Japan, officials closed the pool because the water temperature had reached 95 degrees. “This never happened before in my life as a teacher,” said Harufumi Ishibashi, 47, a vice principal.

Because of the heat, the 2,000 or so construction workers at the site of the new National Stadium — the central venue for the 2020 Summer Olympics in Tokyo — are getting an extra half-hour for their lunch breaks, and free bottles of water, sports drinks and shaved ice.

Koichi Kuromaru, 56, who finished his shift around noon on Wednesday, looked more like he was dressed to hit the ski slopes than to battle the heat. But he opened his jacket to reveal a battery-powered fan stitched into a side pocket, which keeps his upper body cool. Many workers have them.

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Fans at the construction site of the 2020 Olympic stadium. Plans are already being made to keep the most strenuous events out of the heat of the day.CreditIssei Kato/Reuters

Mr. Kuromaru also wore a sweat-wicking shirt and carried a thick cloth he could soak with water and wear under his hard hat.

“Whenever workers feel tired they are told to take breaks,” said Mr. Kuromaru, wiping sweat from his brow with a handkerchief.

The heat has raised concerns about how athletes and spectators will cope during the 2020 Olympics. Average temperatures are likely to continue rising, according to Masahide Kimoto, a professor at the Atmosphere and Ocean Research Institute of the University of Tokyo. “It’s wrong to think that such intense heat that we’ve never seen before will never happen again,” he said.

The Olympic organizers have already released a schedule showing that some of the most rigorous outdoor events will be held early in the morning (the marathon, for example, will start at 7 a.m.). They also plan to install large tents equipped with fans for spectators, and cooling mist showers for athletes at various venues.

For office workers required to wear suits, the extreme heat is something they must simply endure.

“Sometimes clients urge me to take off my necktie,” said Hiroyuki Shigemori, 54, a pharmaceuticals salesman walking into Shimbashi station in Tokyo, his black suit jacket folded over his arm. “I am grateful for that.” (His tie was still on.)

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Just in the past week, 23,000 people were hospitalized for heat-related illnesses.CreditMartin Bureau/Agence France-Presse — Getty Images

When he was a child, Mr. Shigemori recalled, coaches would not let him or his teammates drink water during baseball practice. “We were told it would just make us tired,” he said.

Now, having heard news reports about children collapsing at sports events — a 6-year-old died after a school insect-hunting expedition — he said he worried that children were still being told to “put up with” the heat.

In fact, coaches are making accommodations.

At Hino High School in Tokyo, Masayuki Shimada, the baseball coach, said he had decided to switch the morning warm-up from a long run to laps in the pool. On the first day of summer training, he said, some students had felt sick from the heat.

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A temperature indicator in Kumaya, north of Tokyo. The number would be 105.8 in Fahrenheit.CreditKyodo/Reuters

“It’s time for the team to tone up, but I don’t want to expose them to excessively tough training and invite injury,” Mr. Shimada said. It was the first time in his career he had changed the routine because of extreme heat.

In Kyoto, the high school baseball federation pushed back the starting times of two quarterfinal games to avoid the hottest times of the day. One game started at 7 p.m. and didn’t end until close to 11 p.m.

Walking down a Tokyo street on a clear summer day, you often see a sea of parasols, carried (mostly by women) to block out the sun. Because of the heat this summer, a consortium of local municipalities has set up stalls at zoos, parks and a racetrack where visitors can borrow parasols at no charge.

In the prefecture of Saitama, where the heat record was set this week, local officials have launched a social media campaign to encourage men to carry parasols. “It’s an effective tool for heat and heatstroke,” reads the campaign’s official Twitter account.

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Because of the heat this summer, a consortium of local municipalities has set up stalls at zoos, parks and a racetrack where visitors can borrow parasols at no charge.CreditMartin Bureau/Agence France-Presse — Getty Images